Mercury valve

Fine 4-5.5 Filtration of fine precipitates. As a mercury valve. In extraction apparatus. 

A. 2-tert-Butoxytkiophene. A dry 1-1. three-necked flask is fitted with a mechanical stirrer (Note 1), a reflux condenser having a take-off attachment, and a 250-ml. dropping funnel with a pressure-equalizing side tube.2 A nitrogen-inlet tube is connected to the top of the condenser, and a T-tube branch of this is led to a mercury valve. The latter consists of a U-tube the bend of which is just filled with mercury. 

In a 3-1., three-necked, round-bottomed flask, fitted with a gas inlet tube reaching almost to the bottom, a sealed mechanical stirrer (Note 1), and a gas outlet tube connected to a mercury valve (Note 2), are placed 294 g. (3 moles) of cyclohexanone (Note 3) and 900 ml. of water. After the reaction vessel has been... 

The mercury valve consists of a tube dipping about 0.5 in. into some mercury in a vented test tube. This allows the reaction to be carried out under a slight pressure of chlorine. The checkers found a water valve to be more satisfactory. The outlet tube was made to dip about 7 in. into water in a vented glass tube. A trap (125-ml. suction flask) was placed between the water valve and the reaction flask to prevent water from being sucked into the reaction mixture. 

The hydrogen generator flask A is a similarly shaped Erlenmeyer flask. The inlet adapter to which this flask is attached incorporates a mercury valve D which controls the rate at which the sodium borohydride solution contained in the 250 ml burette G is allowed to flow into the flask A via the syringe needle H (gauge 17 or 19) and the vent holes F in the control valve D. 

Apparatus The apparatus is shown in Fig. 17. It consists essentially of a soda lime column, A, a mercury valve, B, connected through a side arm, C, to a reaction flask, D, by means of a rubber connection. Flask D is a 100-mL round-bottom, long-neck boiling flask, resting in a suitable heating mantle, E. 

Remove the valve and against a constant stream of nitrogen add first tetra-hydrofuran (30 mL) to the flask, then close the tap of the funnel and charge it with a solution of methylenetriphenylphosphorane (5.5 g, 20 mmol)6 in dry tetrahydrofuran (20 mL), and finally reseal the apparatus with the mercury valve. 

Charge a single-necked round-bottomed flask (100 mL) with phosphorane 9 (1.1 g, 1.65 mmol), a magnetic stirrer bar, o-xylene (20 mL), and a catalytic amount of hydroquinone. Furnish with a reflux condenser closed by a mercury valve or a septum/balloon combination and flush the entire set-up with nitrogen. Stir and heat the mixture to 145°C for 10 h. 

Measure 100—200 cc. of the sample into a distillation flask add 12.5—25 cc. of H2O and distil slowly 100-200 cc., depending upon the amount of sample taken, using a mercury valve to prevent loss of alcohol. Exactly neutralize the free acid in 50 cc. of the distillate with 0.1 N alkali and add a measured excess of 25—50 cc. of o. 1 N alkali. Then either boil for an hour under a reflux condenser, cool, and titrate with 0.1 N acid, or allow the soln. to stand over night in a stoppered flask with the excess of alkali, heat with a tube condenser for 30 min. at a temp, below the boiling point, cool, and titrate. Calculate the number of cc. of 0.1 N alkali used in the saponification of the esters as ethyl acetate. 1 cc. of 0.1 N alkali = 0.0088 g. of ethyl acetate. Run a blank, using water in place of the distillate, and make any necessary correction. 

Special precautions to exclude oxygen are rarely taken the ether vapor present over the solution usually suffices to keep the access of air within acceptable limits. Nevertheless, it is sometimes better to replace the air by nitrogen and add a mercury valve, at least at the start of the reaction. An apparatus for carrying out Grignard reactions with exclusion of oxygen has been described by Gilman and Hewlett.105... 

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